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Message-ID: <bca8f865-bc3e-44d7-7298-c2c7e8973580@gmail.com>
Date:   Tue, 15 Mar 2022 18:43:01 +0800
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Subject: Re: [PATCH] fs: erofs: remember if kobject_init_and_add was done
To:     Dongliang Mu <dzm91@hust.edu.cn>, Gao Xiang <xiang@kernel.org>,
        Chao Yu <chao@kernel.org>
Cc:     syzkaller <syzkaller@googlegroups.com>,
        linux-erofs@lists.ozlabs.org,
        Dongliang Mu <mudongliangabcd@gmail.com>,
        linux-kernel@vger.kernel.org
References: <20220315075152.63789-1-dzm91@hust.edu.cn>
From:   Huang Jianan <jnhuang95@gmail.com>
In-Reply-To: <20220315075152.63789-1-dzm91@hust.edu.cn>
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在 2022/3/15 15:51, Dongliang Mu 写道:
> From: Dongliang Mu <mudongliangabcd@gmail.com>
>
> Syzkaller hit 'WARNING: kobject bug in erofs_unregister_sysfs'. This bug
> is triggered by injecting fault in kobject_init_and_add of
> erofs_unregister_sysfs.
>
> Fix this by remembering if kobject_init_and_add is successful.
>
> Note that I've tested the patch and the crash does not occur any more.
>
> Reported-by: syzkaller <syzkaller@googlegroups.com>
> Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
> ---
>   fs/erofs/internal.h | 1 +
>   fs/erofs/sysfs.c    | 9 ++++++---
>   2 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 5aa2cf2c2f80..9e20665e3f68 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -144,6 +144,7 @@ struct erofs_sb_info {
>   	u32 feature_incompat;
>   
>   	/* sysfs support */
> +	bool s_sysfs_inited;

Hi Dongliang,

How about using sbi->s_kobj.state_in_sysfs to avoid adding a extra 
member in sbi ?

Thanks,
Jianan

>   	struct kobject s_kobj;		/* /sys/fs/erofs/<devname> */
>   	struct completion s_kobj_unregister;
>   };
> diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> index dac252bc9228..2b48a4df19b4 100644
> --- a/fs/erofs/sysfs.c
> +++ b/fs/erofs/sysfs.c
> @@ -209,6 +209,7 @@ int erofs_register_sysfs(struct super_block *sb)
>   				   "%s", sb->s_id);
>   	if (err)
>   		goto put_sb_kobj;
> +	sbi->s_sysfs_inited = true;
>   	return 0;
>   
>   put_sb_kobj:
> @@ -221,9 +222,11 @@ void erofs_unregister_sysfs(struct super_block *sb)
>   {
>   	struct erofs_sb_info *sbi = EROFS_SB(sb);
>   
> -	kobject_del(&sbi->s_kobj);
> -	kobject_put(&sbi->s_kobj);
> -	wait_for_completion(&sbi->s_kobj_unregister);
> +	if (sbi->s_sysfs_inited) {
> +		kobject_del(&sbi->s_kobj);
> +		kobject_put(&sbi->s_kobj);
> +		wait_for_completion(&sbi->s_kobj_unregister);
> +	}
>   }
>   
>   int __init erofs_init_sysfs(void)